This invention relates generally to "caseless" or "chamberless" rockets, and, more particularly to a "caseless" rocket which utilizes the passing air as an outer case and as a result thereof burns from the "outside-in".
In the conventional rocket engine a metal chamber or case is employed for housing the propellant system of a rocket under elevated pressures. This chamber or case must be precision made so as to be capable of disassembly and to enable insertion of the propellant grain into the system. Large missiles or rockets are usually composed of two power plants, one called the booster and the other the sustainer. The booster is required to provide a high initial thrust to accelerate the missile from takeoff to a very high velocity in a short period of time. As soon as the booster burns out, it is automatically detached to reduce the flight weight of the missile.
In such present rocket motor applications it is customary to employ an expensive case or housing as set forth hereinabove. This case or housing forms the combustion chamber of the rocket. In most instances an exhaust nozzle is attached to the rearward end and the solid propellant material is placed within the case. In addition, the case or housing must have sufficient strength to handle the loads imposed upon it and at the same time must be as light as possible.
During most of the rocket flight a conventional tactical missile is in supersonic flight. Often it is air dropped at 0.8 Mach and quickly boosted to above Mach 1. Usually with the rocket motors of the past, the initial mass fraction of such a missile is well below 100% with the best mass fraction being at the instant of ignition. This mass fraction, however, continuously and progressively degrades to zero at burn out due to the substantial weight of the case, nozzle assembly and other inert parts. Some improvement in overall system performance is achieved by the booster rockets which are ejected after use, however, even such designs still maintain extremely heavy equipment during flight. During the last quarter of burn time, the propulsion devices heretofore in use are operating at a very poor and decreasing mass fraction in which it is doubtful that any useful benefit is being derived from the inert weights. In fact, the inert weight of conventional tactical missiles are ordinarily an important part of the missile cost and contribute to the manufacturing and quality control complexities. It is therefore extremely important to produce a missile or rocket which can maintain nearly 100% mass fraction at all times during flight and accomplish this at a minimum of expense.